#20 George Kaiser

$12.0 billion

Source: oil & gas, banking

Family fled Nazi Germany 1938, settled in Oklahoma. Parents developed oil and gas business. Took over 1969. Today Kaiser-Francis Oil among the biggest private energy producers. Diversified: owns $1.9 billion stake in Bank of Oklahoma, vast private equity holdings, large derivatives and energy trading portfolio. Sold half of liquefied natural gas outfit Excelerate Energy this year after buying more than $1 billion worth of gas tankers. Passionate philanthropist fights childhood poverty through George Kaiser Family Foundation; helping to develop blighted stretch of Arkansas River. Says billionaire Tom Ward : “He’s one of the most generous and charitable men in the world.